U.S. patent application number 14/017603 was filed with the patent office on 2014-09-25 for power supply circuit and illumination apparatus.
This patent application is currently assigned to Toshiba Lighting & Technology Corporation. The applicant listed for this patent is Toshiba Lighting & Technology Corporation. Invention is credited to Hiroshi Akahoshi, Noriyuki Kitamura, Hirokazu Otake, Yuji Takahashi.
Application Number | 20140285099 14/017603 |
Document ID | / |
Family ID | 49080814 |
Filed Date | 2014-09-25 |
United States Patent
Application |
20140285099 |
Kind Code |
A1 |
Akahoshi; Hiroshi ; et
al. |
September 25, 2014 |
Power Supply Circuit and Illumination Apparatus
Abstract
According to one embodiment, there is provided a power supply
circuit including a power conversion unit, a current regulator, a
controller, and a controller power supply. The power conversion
unit converts an AC voltage with a controlled conduction angle into
a different voltage. The current regulator includes a branch path
electrically connected to the power supply path and switches
between a first state in which a part of a current flowing through
the power supply path flows to the branch path and a second state
in which a current flowing to the branch path is lower than that of
the first state. The controller switches the current regulator to
the second state in at least a part of a conduction period of a
detected conduction angle and switches the current regulator to the
first state in a blocking period of the detected conduction
angle.
Inventors: |
Akahoshi; Hiroshi;
(Yokosuka-shi, JP) ; Otake; Hirokazu;
(Yokosuka-shi, JP) ; Kitamura; Noriyuki;
(Yokosuka-shi, JP) ; Takahashi; Yuji;
(Yokosuka-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Toshiba Lighting & Technology Corporation |
Yokosuka-shi |
|
JP |
|
|
Assignee: |
Toshiba Lighting & Technology
Corporation
Yokosuka-shi
JP
|
Family ID: |
49080814 |
Appl. No.: |
14/017603 |
Filed: |
September 4, 2013 |
Current U.S.
Class: |
315/200R ;
363/44; 363/53; 363/89 |
Current CPC
Class: |
H05B 45/37 20200101;
Y02B 20/347 20130101; H02M 7/217 20130101; H02M 1/32 20130101; H05B
45/60 20200101; Y02B 20/30 20130101; H02M 1/126 20130101 |
Class at
Publication: |
315/200.R ;
363/89; 363/44; 363/53 |
International
Class: |
H05B 33/08 20060101
H05B033/08; H02M 1/12 20060101 H02M001/12; H02M 1/32 20060101
H02M001/32; H02M 7/217 20060101 H02M007/217 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 22, 2013 |
JP |
2013-061116 |
Claims
1. A power supply circuit comprising: a power conversion unit that
converts an AC voltage with a controlled conduction angle, supplied
through a power supply path, into a different voltage and supplies
the converted voltage to a load; a current regulator that includes
a branch path electrically connected to the power supply path and
can switch between a first state in which a part of a current
flowing through the power supply path flows to the branch path and
a second state in which a current flowing to the branch path is
lower than that of the first state; a controller that detects a
conduction angle of the AC voltage and controls the switching of
the current regulator between the first state and the second state
based on the detected conduction angle; and a controller power
supply that is electrically connected to the branch path, converts
a voltage, supplied through the branch path, into a driving voltage
corresponding to the controller, and supplies the driving voltage
to the controller, the controller switching the current regulator
to the second state in at least a part of a conduction period of
the detected conduction angle and switching the current regulator
to the first state in a blocking period of the detected conduction
angle.
2. The circuit according to claim 1, wherein the controller power
supply includes a capacitor that is connected in parallel to an
output path through which the driving voltage is output to the
controller and that smoothes the driving voltage.
3. The circuit according to claim 2, wherein the current regulator
includes a switching device that is electrically connected to the
power supply path and switches between the first state and the
second state by switching on and off the switching device.
4. The circuit according to claim 3, wherein the controller power
supply includes a constant power circuit that decreases a current
flowing to the branch path along with an increase in the absolute
value of the AC voltage and increases a current flowing to the
branch path along with a decrease in the absolute value of the AC
voltage.
5. The circuit according to claim 1, wherein the power conversion
unit includes an AC-DC converter and a DC-DC converter, the AC-DC
converter converts the AC voltage into a first DC voltage, and the
DC-DC converter converts the first DC voltage into a second DC
voltage and supplies the second DC voltage to the load.
6. The circuit according to claim 1, wherein the power conversion
unit includes a filter capacitor that is connected to the power
supply path in parallel.
7. The circuit according to claim 1, further comprising an
overcurrent protection unit that suppresses a current flowing to
the load, wherein the controller controls an operation of the
overcurrent protection unit.
8. The circuit according to claim 7, wherein the controller inputs
a dimming signal corresponding to the detected conduction angle to
the overcurrent protection unit, and the overcurrent protection
unit detects a current flowing to the load and performs feedback
control of the power conversion unit based on the dimming signal
and the detected current.
9. The circuit according to claim 2, wherein the controller power
supply further includes a regulator, and the regulator generates
the driving voltage from a DC voltage, smoothed by the capacitor,
and outputs the driving voltage to the controller.
10. The circuit according to claim 9, wherein a capacity of the
capacitor is 10 .mu.F to 20 .mu.F.
11. The circuit according to claim 1, wherein a detection voltage
for detecting an absolute value of the AC voltage is input to the
controller, and the controller determines a period in which the
detection voltage is higher than or equal to a threshold voltage as
a conduction period, determines a period in which the detection
voltage is lower than the threshold voltage as a blocking period,
and detects the conduction angle based on a ratio of the conduction
period and the blocking period.
12. The circuit according to claim 11, wherein the controller
detects, based on the detection voltage, whether the conduction
angle of the AC voltage is controlled by phase control or reverse
phase control.
13. The circuit according to claim 12, wherein when the conduction
angle of the AC voltage is controlled by the phase control, the
controller delays a time when the current regulator is switched
from the first state to the second state to be slower by a first
micro time than a time when a voltage value of the detection
voltage is switched from the state of being lower than the
threshold voltage to the state of being higher than or equal to the
threshold voltage.
14. The circuit according to claim 12, wherein when the conduction
angle of the AC voltage is controlled by the reverse phase control,
the controller advances a time when the current regulator is
switched from the second state to the first state to be faster by a
second micro time than a time when a voltage value of the detection
voltage is switched from the state of being higher than or equal to
the threshold voltage to the state of being lower than the
threshold voltage.
15. The circuit according to claim 1, wherein the load is an
illumination load including an illumination light source.
16. The circuit according to claim 15, wherein the illumination
light source is a light-emitting diode.
17. The circuit according to claim 1, wherein the current regulator
includes a switching device that is electrically connected to the
power supply path and switches between the first state and the
second state by switching on and off the switching device.
18. The circuit according to claim 17, wherein the controller power
supply includes a constant power circuit that decreases a current
flowing to the branch path along with an increase in the absolute
value of the AC voltage and increases a current flowing to the
branch path along with a decrease in the absolute value of the AC
voltage.
19. The circuit according to claim 1, wherein the controller power
supply includes a constant power circuit that decreases a current
flowing to the branch path along with an increase in the absolute
value of the AC voltage and increases a current flowing to the
branch path along with a decrease in the absolute value of the AC
voltage.
20. An illumination apparatus comprising: an illumination load; and
a power supply circuit that supplies power to the illumination
load, the power supply circuit including: a power conversion unit
that converts an AC voltage with a controlled conduction angle,
supplied through a power supply path, into a different voltage and
supplies the converted voltage to a load, a current regulator that
includes a branch path electrically connected to the power supply
path, can switch between a first state in which a part of a current
flowing through the power supply path flows to the branch path and
a second state in which a current flowing to the branch path is
lower than that of the first state, a controller that detects a
conduction angle of the AC voltage and controls the switching of
the current regulator between the first state and the second state
based on the detected conduction angle, and a controller power
supply that is electrically connected to the branch path, converts
a voltage, supplied through the branch path, into a driving voltage
corresponding to the controller, and supplies the driving voltage
to the controller, and the controller switches the current
regulator to the second state in at least a part of a conduction
period of the detected conduction angle and switches the current
regulator to the first state in a blocking period of the detected
conduction angle.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from Japanese Patent Application No. 2013-061116, filed on
Mar. 22, 2013; the entire contents of which are incorporated herein
by reference.
FIELD
[0002] Embodiments described herein relate generally to a power
supply circuit and an illumination apparatus.
BACKGROUND
[0003] In an illumination apparatus, an illumination light source
is shifted from an incandescent lamp or a fluorescent lamp to a
power-saving and long-life light source such as a light-emitting
element including a light-emitting diode (LED). For a power supply
circuit which supplies power to such a light source, the
suppression of power loss is desired.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a block diagram schematically illustrating an
illumination apparatus according to an embodiment;
[0005] FIG. 2 is a circuit diagram schematically illustrating a
power supply circuit according to an embodiment;
[0006] FIGS. 3A and 3B are graphs illustrating an operation of a
controller according to an embodiment;
[0007] FIGS. 4A to 4C are graphs schematically illustrating an
operation of a controller according to an embodiment; and
[0008] FIGS. 5A to 5C are graphs schematically illustrating an
operation of a controller according to an embodiment.
DETAILED DESCRIPTION
[0009] According to one embodiment, there is provided a power
supply circuit including a power conversion unit, a current
regulator, a controller, and a controller power supply. The power
conversion unit converts an AC voltage with a controlled conduction
angle, supplied through a power supply path, into a different
voltage and supplies the converted voltage to a load. The current
regulator includes a branch path electrically connected to the
power supply path and can switch between a first state in which a
part of a current flowing through the power supply path flows to
the branch path and a second state in which a current flowing to
the branch path is lower than that of the first state. The
controller detects a conduction angle of the AC voltage and
controls the switching of the current regulator between the first
state and the second state based on the detected conduction angle.
The controller power supply is electrically connected to the branch
path, converts a voltage, supplied through the branch path, into a
driving voltage corresponding to the controller, and supplies the
driving voltage to the controller. The controller switches the
current regulator to the second state in at least a part of a
conduction period of the detected conduction angle and switches the
current regulator to the first state in a blocking period of the
detected conduction angle.
[0010] According to another embodiment, there is provided an
illumination apparatus including an illumination load and a power
supply circuit. The power supply circuit supplies power to the
illumination load. The power supply circuit includes a power
conversion unit, a current regulator, a controller, and a
controller power supply. The power conversion unit converts an AC
voltage with a controlled conduction angle, supplied through a
power supply path, into a different voltage and supplies the
converted voltage to a load. The current regulator includes a
branch path electrically connected to the power supply path and can
switch between a first state in which a part of a current flowing
through the power supply path flows to the branch path and a second
state in which a current flowing to the branch path is lower than
that of the first state. The controller detects a conduction angle
of the AC voltage and controls the switching of the current
regulator between the first state and the second state based on the
detected conduction angle. The controller power supply is
electrically connected to the branch path, converts a voltage,
supplied through the branch path, into a driving voltage
corresponding to the controller, and supplies the driving voltage
to the controller. The controller switches the current regulator to
the second state in at least a part of a conduction period of the
detected conduction angle and switches the current regulator to the
first state in a blocking period of the detected conduction
angle.
[0011] Hereinafter, each embodiment will be described with
reference to the drawings.
[0012] The drawings are schematic or conceptual, and a relationship
between the thickness and the width of each portion, size ratios
between portions, and the like are not necessarily limited to being
the same as those of actual ones. In addition, even when the same
portion is illustrated in the drawings, the dimension, ratio, and
the like thereof may vary depending on the drawings.
[0013] In this specification and the respective drawings, the same
elements are represented by the same reference numerals, and the
description thereof will not be repeated.
[0014] FIG. 1 is a block diagram schematically illustrating an
illumination apparatus according to an embodiment.
[0015] As illustrated in FIG. 1, an illumination apparatus 10
includes an illumination load 12 (load) and a power supply circuit
14. The illumination load 12 includes an illumination light source
16 such as a light-emitting diode (LED). The illumination light
source 16 may be an organic light-emitting diode (OLED) or the
like. As the illumination light source 16, for example, a
light-emitting element having forward voltage drop is used. The
illumination load 12 turns on the illumination light source 16 by
the application of an output voltage and the supply of an output
current from the power supply circuit 14. Values of the output
voltage and the output current are determined according to the
illumination light source 16.
[0016] The power supply circuit 14 is connected to an AC power
supply 2 and a dimmer 3. In this specification, "connection" refers
to electrical connection and includes cases where elements are not
physically connected to each other and cases where elements are
connected to each other through another element.
[0017] The AC power supply 2 is, for example, a commercial power
supply. The dimmer 3 generates an AC voltage VCT with a controlled
conduction angle from an AC power supply voltage VIN of the AC
power supply 2. The power supply circuit 14 converts the AC voltage
VCT, supplied from the dimmer 3, into a DC voltage and outputs the
DC voltage to the illumination load 12 to turn on the illumination
light source 16. In addition, the power supply circuit 14 dims the
illumination light source 16 in synchronization with the AC voltage
VCT with a controlled conduction angle. The dimmer 3 is provided as
necessary and may not be provided. When the dimmer 3 is not
provided, the power supply voltage VIN of the AC power supply 2 is
supplied to the power supply circuit 14.
[0018] Examples of a method of controlling a conduction angle using
the dimmer 3 include phase control (leading edge control) of
controlling a conduction phase in a period from a zero-cross point
of an AC voltage to a point at which an absolute value of the AC
voltage is maximum; and reverse phase control (trailing edge
control) of controlling a blocking phase in a period from a point
at which an absolute value of an AC voltage is maximum to a
zero-cross point of the AC voltage.
[0019] The phase control dimmer 3 has the following
characteristics, for example. The circuit configuration is simple,
and a relatively high electrical load can be handled. However, when
a triac is used, a low-load operation is difficult to perform.
Therefore, when so-called power supply dipping in which a power
supply voltage is temporarily decreased occurs, the operation is
likely to be unstable. In addition, when a capacitive load is
connected, an inrush current is generated. Therefore, compatibility
with a capacitive load is low.
[0020] On the other hand, the reverse phase control dimmer 3 has
the following characteristics, for example. The operation can be
performed at a low load; even when a capacitive load is connected,
an inrush current is not generated; and even when power supply
dipping occurs, the operation is stable. However, since the circuit
configuration is complicated and the temperature is likely to rise,
the reverse phase control dimmer 3 is not suitable to a high load.
In addition, when an inductive load is connected, a surge is
generated.
[0021] In this embodiment, a configuration in which the dimmer 3 is
connected in series between terminals 4 and 6 of a pair of power
supply lines through which the power supply voltage VIN is supplied
is described as an example. However, other configurations may also
be adopted.
[0022] The power supply circuit 14 includes a power conversion unit
21, a controller 22, a current regulator 23, a controller power
supply 24, and an overcurrent protection unit 25.
[0023] The power conversion unit 21 converts the AC voltage VCT
with a controlled conduction angle, supplied through a first power
supply path 26a, into a different voltage and supplies the
converted voltage to the illumination load 12. The power conversion
unit 21 includes an AC-DC converter 21a and a DC-DC converter 21b.
The AC-DC converter 21a converts the AC voltage VCT, supplied
through the first power supply path 26a, into a first DC voltage
VDC1.
[0024] The DC-DC converter 21b is connected to the AC-DC converter
21a through a second power supply path 26b. The DC-DC converter 21b
converts the first DC current VDC1, supplied from the second power
supply path 26b, into a second DC voltage VDC2 having a
predetermined voltage value corresponding to the illumination load
12; and supplies the second DC voltage VDC2 to the illumination
load 12. The absolute value of the second DC voltage VDC2 is
different from the absolute value of the first DC voltage VDC1. For
example, the absolute value of the second DC voltage VDC2 is lower
than the absolute value of the first DC voltage VDC1. In this
example, the DC-DC converter 21b is a step-down converter. By the
supply of the second DC voltage VDC2, the illumination light source
16 of the illumination load 12 is turned on.
[0025] The current regulator 23 includes a branch path 27
electrically connected to the first power supply path 26a and
switches between a first state in which a part of a current flowing
to the first power supply path 26a flows to the branch path 27 and
a second state in which a current flowing through the branch path
27 is lower than that of the first state. As a result, the current
regulator 23 regulates, for example, a current flowing to the first
power supply path 26a. The branch path 27 includes, for example, a
first branch line 27a that is connected to an input terminal 4; and
a second branch line 27b that is connected to an input terminal 5.
In the second state, for example, a current does not substantially
flow to the branch path 27. For example, the first state is the
conduction state, and the second state is the non-conduction state.
In the second state, a small current which has no effect on the
operation may flow to the branch path 27. The branch path 27 may be
connected to, for example, the second power supply path 26b.
[0026] The controller power supply 24 includes a distribution unit
28 that is connected to the current regulator 23. The controller
power supply 24 converts a voltage, input through the current
regulator 23 and the distribution unit 28, into a DC driving
voltage VDD corresponding to the controller 22; and supplies the
driving voltage VDD to the controller 22.
[0027] The controller 22 detects a conduction angle of the AC
voltage VCT. The controller 22 generates a dimming signal DMS
corresponding to the detected conduction angle and inputs the
dimming signal DMS to the overcurrent protection unit 25. In
addition, the controller 22 generates a control signal CGS
according to the detected conduction angle and inputs the control
signal CGS to the current regulator 23. As a result, the controller
22 controls the switching of the current regulator 23 between the
first state and the second state. In this way, by controlling the
current regulator 23 and the overcurrent protection unit 25
according to the detected conduction angle, the controller 22 dims
the illumination light source 16 in synchronization with the
conduction angle control of the dimmer 3. As the controller 22, for
example, a microprocessor may be used.
[0028] The overcurrent protection unit 25 is connected to an output
terminal 8 of the power supply circuit 14 on the low potential
side. That is, the overcurrent protection unit 25 is connected to
an end of the illumination load 12 on the low potential side. The
overcurrent protection unit 25 detects a current flowing to the
illumination load 12 (illumination light source 16). The
overcurrent protection unit 25 performs feedback control of the
DC-DC converter 21b based on the dimming signal DMS input from the
controller 22 and the detected current. For example, when an
overcurrent flows to the illumination light source 16, the
overcurrent protection unit 25 performs the feedback control of the
DC-DC converter 21b to decrease the current. As a result, the
overcurrent protection unit 25 inhibits an overcurrent from flowing
to the illumination light source 16.
[0029] FIG. 2 is a circuit diagram schematically illustrating a
power supply circuit according to an embodiment.
[0030] As illustrated in FIG. 2, the AC-DC converter 21a includes a
rectifier circuit 30, a smoothing capacitor 32, an inductor 34, and
a filter capacitor 36.
[0031] The rectifier circuit 30 is, for example, a diode bridge.
Input terminals 30a and 30b of the rectifier circuit 30 are
connected to a pair of the input terminals 4 and 5. The AC voltage
VCT subjected to phase control or reverse phase control by the
dimmer 3 is input to the input terminals 30a and 30b of the
rectifier circuit 30. For example, the rectifier circuit 30
performs full-wave rectification on the AC voltage VCT and
generates a ripple voltage after the full-wave rectification
between a high potential terminal 30c and a low potential terminal
30d.
[0032] The smoothing capacitor 32 is connected between the high
potential terminal 30c and the low potential terminal 30d of the
rectifier circuit 30. The smoothing capacitor 32 smoothes a ripple
voltage which is rectified by the rectifier circuit 30. As a
result, the first DC current VDC1 appears on both ends of the
smoothing capacitor 32.
[0033] The inductor 34 is connected to the input terminal 4 in
series. For example, the inductor 34 is connected to the first
power supply path 26a in series. The filter capacitor 36 is
connected between the input terminals 4 and 5. For example, the
filter capacitor 36 is connected to the first power supply path 26a
in parallel. The inductor 34 and the filter capacitor 36 remove
noise which is included in, for example, the AC voltage VCT.
[0034] The DC-DC converter 21b is connected to both ends of the
smoothing capacitor 32. As a result, the first DC voltage VDC1 is
input to the DC-DC converter 21b. The DC-DC converter 21b converts
the first DC voltage VDC1 into the second DC voltage VDC2 having a
different absolute value and outputs the second DC voltage VDC2 to
output terminals 7 and 8 of the power supply circuit 14. The
illumination load 12 is connected to the output terminals 7 and 8.
The illumination load 12 turns on the illumination light source 16
through the second DC voltage VDC2 supplied from the power supply
circuit 14.
[0035] For example, the current regulator 23 includes rectifying
devices 41 and 42, resistors 43 and 44, a zener diode 45, and
switching devices 46 and 47.
[0036] The rectifying devices 41 and 42 are, for example, diodes.
An anode of the rectifying device 41 is connected to the input
terminal 30a of the rectifier circuit 30 through the first branch
line 27a. An anode of the rectifying device 42 is connected to the
input terminal 30b of the rectifier circuit 30 through the second
branch line 27b.
[0037] As the switching device 46, for example, FET or GaN-HEMT may
be used. In the following description, the switching device 46 is
assumed as FET. In addition, in this example, the switching device
46 is normally-off type. The switching device 46 may also be
normally-on type.
[0038] A drain of the switching device 46 is connected to a cathode
of the rectifying device 41 and a cathode of the rectifying device
42. That is, the drain of the switching device 46 is connected to
the first power supply path 26a through the rectifying devices 41
and 42. A gate of the switching device 46 is connected to an end of
the resistor 43 and a cathode of the zener diode 45. The other end
of the resistor 43 is connected to the cathode of the rectifying
device 41 and the cathode of the rectifying device 42. An anode of
the zener diode 45 is connected to the low potential terminal 30d
of the rectifier circuit 30.
[0039] Along with the application of the AC voltage VCT, a current
having one polarity flows to the drain of the switching device 46
through the rectifying device 41. Along with the application of the
AC voltage VCT, a current having the other polarity flows to the
drain of the switching device 46 through the rectifying device 42.
As a result, a ripple voltage after the full-wave rectification of
the AC voltage VCT is applied to the drain of the switching device
46.
[0040] A ripple voltage is applied to the cathode of the zener
diode 45 through the resistor 43 and the respective rectifying
devices 41 and 42. As a result, a substantially constant voltage
corresponding to a breakdown voltage of the zener diode 45 is
applied to the gate of the switching device 46. Accordingly, a
substantially constant current flows between the drain and a source
of the switching device 46. In this way, the switching device 46
functions as a constant current device. For example, the switching
device 46 regulates a current flowing to the branch path 27.
[0041] In this example, the switching device 47 is an n-p-n
transistor. The switching device 47 is normally-off type. For
example, the switching device 47 may be FET or GaN-HEMT. The
switching device 47 may also be normally-on type.
[0042] A collector of the switching device 47 is connected to the
gate of the switching device 46. An emitter of the switching device
47 is connected to the low potential terminal 30d of the rectifier
circuit 30. A base of the switching device 47 is connected to an
end of the resistor 44. The other end of the resistor 44 is
connected to the controller 22. That is, the base of the switching
device 47 is connected to the controller 22 through the resistor
44.
[0043] The controller 22 inputs the control signal CGS to the base
of the switching device 47. For example, by switching the control
signal CGS, input from the controller 22, from Lo to Hi, the
switching device 47 is switched from the off state to the on
state.
[0044] When the switching device 47 is switched on, the gate of the
switching device 46 is set to a potential of the low potential
terminal 30d of the rectifier circuit 30. As a result, the
switching device 46 is switched off. That is, by switching on the
switching device 47, the current regulator 23 is switched to the
second state; and by switching off the switching device 47, the
current regulator 23 is switched to the first state.
[0045] For example, the controller power supply 24 includes a
rectifying device 51, a resistor 52, a regulator 53, and a backup
capacitor (capacitor) 54.
[0046] An anode of the rectifying device 51 is connected to the
source of the switching device 46. A cathode of the rectifying
device 51 is connected to an end of the resistor 52. The other end
of the resistor 52 is connected to an input terminal of the
regulator 53. In addition, the other end of the resistor 52 is also
connected to an end of the backup capacitor 54. The other end of
the backup capacitor 54 is connected to the low potential terminal
30d of the rectifier circuit 30. An output terminal of the
regulator 53 is connected to the controller 22.
[0047] When the current regulator 23 is in the first state, a
ripple voltage is input from the first power supply path 26a to the
backup capacitor 54 through the switching device 46, the rectifying
device 51, and the resistor 52, thereby charging the backup
capacitor 54. The backup capacitor 54 may be charged by the
smoothing capacitor 32. At the same time, a substantially DC
voltage, which is obtained by the backup capacitor 54 smoothing a
ripple voltage from the first power supply path 26a, is input to
the regulator 53. The regulator 53 generates the substantially
constant DC driving voltage VDD from the input DC voltage and
outputs the driving voltage VDD to the controller 22. As a result,
the driving voltage VDD is supplied to the controller 22. In this
way, the backup capacitor 54 is connected in parallel to an output
path through which the driving voltage VDD is output to the
controller 22; and smoothes the driving voltage VDD.
[0048] In addition, when the current regulator 23 is switched from
the first state to the second state, charges accumulated in the
backup capacitor 54 are supplied to the regulator 53. As a result,
when the current regulator 23 is in the second state, the
controller 22 may be temporarily driven by the charges accumulated
in the backup capacitor 54. The capacity of the backup capacitor 54
is, for example, approximately 10 .mu.F to 20 .mu.F.
[0049] On the controller power supply 24, resistors 55 and 56 and a
capacitor 57 are further provided. An end of the resistor 55 is
connected to the respective cathodes of the rectifying devices 41
and 42. The other end of the resistor 55 is connected to an end of
the resistor 56. The other end of the resistor 56 is connected to
the low potential terminal 30d of the rectifier circuit 30. The
capacitor 57 is connected to the resistor 56 in parallel. A
connection point between the resistors 55 and 56 is connected to
the controller 22. As a result, a voltage corresponding to a
voltage dividing ratio of the resistors 55 and 56 is input to the
controller 22 as a detection voltage for detecting the absolute
value of the AC voltage VCT.
[0050] For example, based on the detection voltage, the controller
22 detects whether the conduction angle of the AC voltage VCT is
controlled or not; and the type of the conduction angle control
(phase control or reverse phase control). When the conduction angle
is controlled, the controller 22 detects the conduction angle.
Based on the detection result, the controller 22 generates the
dimming signal DMS and inputs the dimming signal DMS to the
overcurrent protection unit 25. For example, the controller 22
inputs a PWM signal corresponding to the detected conduction angle
to the overcurrent protection unit 25 as the dimming signal
DMS.
[0051] In addition, a constant power circuit 58 is provided on the
controller power supply 24. For example, the constant power circuit
58 includes a semiconductor device 60, resistors 61 to 65, a
capacitor 66, and a shunt regulator 67. In this example, the
semiconductor device 60 is an npn transistor. The semiconductor
device 60 is normally-off type. As the semiconductor device 60, for
example, FET or GaN-HEMT may be used. The semiconductor device 60
may also be normally-on type.
[0052] A collector of the semiconductor device 60 is connected to
the source of the switching device 46. A base of the semiconductor
device 60 is connected to an end of the resistor 61, an end of the
resistor 62, and a cathode of the shunt regulator 67. An emitter of
the semiconductor device 60 is connected to an end of the resistor
65. The other end of the resistor 61 is connected to the collector
of the semiconductor device 60. The other end of the resistor 62 is
connected to a reference terminal of the shunt regulator 67. The
other end of the resistor 65 is connected to the low potential
terminal 30d of the rectifier circuit 30.
[0053] An end of the resistor 63 is connected to the respective
cathodes of the rectifying devices 41 and 42. The other end of the
resistor 63 is connected to an end of the resistor 64. The other
end of the resistor 64 is connected to the low potential terminal
30d of the rectifier circuit 30. A connection point between the
resistor 63 and the resistor 64 is connected to the reference
terminal of the shunt regulator 67. As a result, a voltage, which
is obtained by the resistors 63 and 64 dividing a ripple voltage
from the first power supply path 26a, is input to the reference
terminal of the shunt regulator 67 as a reference voltage. The
capacitor 66 is connected to the resistor 64 in parallel. An anode
of the shunt regulator 67 is connected to the low potential
terminal 30d of the rectifier circuit 30.
[0054] In the controller power supply 24, a base potential of the
semiconductor device 60 changes depending on the ripple voltage
which is input to the reference terminal of the shunt regulator 67.
That is, the base potential of the semiconductor device 60 changes
depending on the root-mean-square of the AC voltage VCT. For
example, when the absolute value of the AC voltage VCT is maximum,
the base potential of the semiconductor device 60 is maximum.
[0055] When the base potential of the semiconductor device 60
increases, a collector current of the semiconductor device 60
increases, and a source potential of the switching device 46
increases. That is, the controller power supply 24 changes the
source potential of the switching device 46 depending on the
absolute value of the AC voltage VCT. Since a gate potential of the
switching device 46 is substantially constant, a drain current of
the switching device 46 can be changed by changing the source
potential. Specifically, by increasing the source potential, the
drain current decreases; and by reducing the source potential, the
drain current increases.
[0056] Accordingly, when the absolute value of the AC voltage VCT
is high, the drain current of the switching device 46 decreases;
and when the absolute value of the AC voltage VCT is low, the drain
current of the switching device 46 increases.
[0057] In this way, the constant power circuit 58 decreases a
current flowing to the branch path 27 along with an increase in the
absolute value of the AC voltage VCT and increases a current
flowing to the branch path 27 along with a decrease in the absolute
value of the AC voltage VCT. As a result, for example, the power
consumed in the controller power supply 24 can be made
substantially constant. The power being substantially constant
refers to the state in which the power consumed in the controller
power supply 24 is within a predetermined error range.
[0058] The overcurrent protection unit 25 includes a differential
amplifier circuit 70 and a semiconductor device 71. In this
example, the semiconductor device 71 is an npn transistor. The
semiconductor device 71 is normally-off type. The semiconductor
device 71 may be, for example, a pnp transistor or FET. The
semiconductor device 71 may also be normally-on type.
[0059] For example, the differential amplifier circuit 70 includes
an operational amplifier 72 and a capacitor 73. The capacitor 73 is
connected between an output terminal of the operational amplifier
72 and an inverted input terminal of the operational amplifier
72.
[0060] A non-inverted input terminal of the operational amplifier
72 is connected to the output terminal 8. That is, the non-inverted
input terminal of the operational amplifier 72 is connected to an
end of the illumination load 12 on the low potential side. As a
result, a current flowing to the illumination light source 16 can
be detected. When a light-emitting element such as an LED is used
as the illumination light source 16, a voltage of the illumination
light source 16 is substantially constant according to forward
voltage drop. Accordingly, when a light-emitting element such as an
LED is used as the illumination light source 16, a current flowing
to the illumination light source 16 can be appropriately detected
by the connection to the end of the illumination load 12 on the low
potential side.
[0061] The inverted input terminal of the operational amplifier 72
is connected to an end of a resistor 74. The other end of the
resistor 74 is connected to an end of a resistor 75, an end of a
capacitor 76, and an end of a resistor 77. The other end of the
resistor 75 and the other end of the capacitor 76 are connected to
the low potential terminal 30d of the rectifier circuit 30. The
other end of the resistor 77 is connected to the controller 22. In
this way, the inverted input terminal of the operational amplifier
72 is connected to the controller 22 through the resistors 74 and
77. The dimming signal DMS is input from the controller 22 to the
inverted input terminal of the operational amplifier 72.
[0062] For example, a DC voltage, which is obtained by the
capacitor 76 smoothing the PWM signal, is input to the inverted
input terminal of the operational amplifier 72 as the dimming
signal DMS. For example, a DC voltage corresponding to a dimming
degree of the dimmer 3 is input to the inverted input terminal of
the operational amplifier 72 as the dimming signal DMS. A voltage
level of the dimming signal DMS is set according to a voltage level
of the detection voltage which is input to the non-inverted input
terminal. More specifically, for example, a voltage level of the
dimming signal DMS corresponding to a desired dimming degree is set
so as to be substantially the same as a voltage level of the
detection voltage of a case where the illumination light source 16
emits light with a luminance corresponding to the dimming
degree.
[0063] In this way, the detection voltage corresponding to a
current flowing to the illumination light source 16 is input to the
non-inverted input terminal of the operational amplifier 72, and
the dimming signal DMS is input to the inverted input signal of the
operational amplifier 72. As a result, a signal corresponding to a
difference between the detection voltage and the dimming signal DMS
is output from the output terminal of the operational amplifier 72.
As the detection voltage becomes higher than the dimming signal
DMS, an output of the operational amplifier 72 increases. That is,
when an overcurrent flows to the illumination light source 16, the
output of the operational amplifier 72 increases. In this way, in
this example, the dimming signal DMS is used as a reference value.
When dimming is not performed, a substantially constant DC voltage
which is a reference value may be input to the inverted input
terminal of the operational amplifier 72.
[0064] A collector of the semiconductor device 71 is connected to
the DC-DC converter 21b. An emitter of the semiconductor device 71
is connected to the low potential terminal 30d of the rectifier
circuit 30. A base of the semiconductor device 71 is connected to
the output terminal of the operational amplifier 72. As a result, a
collector current of the semiconductor device 71 is controlled by
the output from the operational amplifier 72.
[0065] As described above, when the detection voltage is higher
than the dimming signal DMS, the output of the operational
amplifier 72 increases. Accordingly, for example, when the
detection voltage is higher than the dimming signal DMS, the
semiconductor device 71 is switched on; and when the detection
voltage is lower than or equal to the dimming signal DMS, the
semiconductor device 71 is switched off. For example, as the
detection voltage becomes higher than the dimming signal DMS, the
collector current of the semiconductor device 71 increases.
[0066] When the semiconductor device 71 is switched on, the DC-DC
converter 21b stops the power supply to the illumination load 12.
As a result, an overcurrent can be inhibited from flowing to the
illumination light source 16.
[0067] FIGS. 3A and 3B are graphs illustrating an operation of a
controller according to an embodiment.
[0068] For example, the controller 22 is activated in response to
the supply of the driving voltage VDD from the controller power
supply 24 and determines the control type of the dimmer 3 based on
the detection voltage.
[0069] In FIGS. 3A and 3B, the horizontal axis represents the time
(t); and the vertical axis represents the detection voltage
Vdet.
[0070] FIG. 3A illustrates a waveform example of the detection
voltage Vdet when the AC voltage VCT is supplied from the phase
control dimmer 3.
[0071] FIG. 3B illustrates a waveform example of the detection
voltage Vdet when the AC voltage VCT is supplied from the reverse
phase control dimmer 3.
[0072] As illustrated in FIGS. 3A and 3B, the controller 22 sets a
first threshold voltage Vth1 and a second threshold voltage Vth2
for the detection voltage Vdet. The absolute value of the second
threshold voltage Vth2 is higher than the absolute value of the
first threshold voltage Vth1. The first threshold voltage Vth1 is,
for example, approximately 1 V. The second threshold voltage Vth2
is, for example, approximately 3 V.
[0073] The controller 22 keeps a time dt until the detection
voltage Vdet reaches the second threshold voltage Vth2 after the
detection voltage Vdet reaches the first threshold voltage Vth1.
The controller 22 acquires a gradient dV/dt from a difference dV
between the first threshold voltage Vth1 and the second threshold
voltage Vth2; and the time dt. The controller 22 determines whether
the gradient dV/dt is higher than or equal to a predetermined
value; determines the type of the conduction angle control as phase
control when the gradient dV/dt is higher than or equal to the
predetermined value; and determines the type of the conduction
angle control as reverse phase control when the gradient dV/dt is
lower than the predetermined value. In order to keep the time dt,
for example, an internal clock may be used, or a timer or the like
may be provided outside the apparatus.
[0074] The controller 22 regularly performs the determination until
the input of the power supply voltage VIN or the AC voltage VCT
stops. The determination may be performed, for example, on a
half-wave basis of the power supply voltage VIN or the AC voltage
VCT or on a half-wave basis of a predetermined number.
[0075] FIGS. 4A to 4C are graphs illustrating an operation of a
controller according to an embodiment.
[0076] FIGS. 4A to 4C illustrate an operation example of the
controller 22 when the type of the conduction angle control is
determined as phase control.
[0077] In FIGS. 4A to 4C, the horizontal axis represents the time
t.
[0078] In FIG. 4A, the vertical axis represents the detection
voltage Vdet.
[0079] In FIG. 4B, the vertical axis represents a voltage value of
the control signal CGS.
[0080] In FIG. 4C, the vertical axis represents a voltage which is
input to the controller power supply 24.
[0081] As illustrated in FIGS. 4A to 4C, when the controller 22
determines the type of the conduction angle control as phase
control, the controller 22 detects the conduction angle of the AC
voltage VCT based on the determination result. For example, the
controller 22 determines a period in which the detection voltage
Vdet is higher than or equal to the first threshold voltage Vth1 as
a conduction period Ton for the conduction angle control of the
dimmer 3. In addition, the controller 22 determines a period in
which the detection voltage Vdet is lower than the first threshold
voltage Vth1 as a blocking period Toff for the conduction angle
control of the dimmer 3. As a result, the controller 22 detects the
conduction angle of the AC voltage VCT based on a ratio of the
conduction period Ton and the blocking period Toff. The conduction
angle may be detected based on the second threshold voltage Vth2.
The conduction angle may be detected based on a threshold different
from the first threshold voltage Vth1 and the second threshold
voltage Vth2.
[0082] After detecting the conduction angle of the AC voltage VCT,
the controller 22 generates the dimming signal DMS with a duty
ratio corresponding to the conduction angle and inputs the
generated dimming signal DMS to the overcurrent protection unit 25.
As a result, the illumination light source 16 is dimmed according
to the AC voltage VCT of which the conduction angle is controlled
by phase control.
[0083] In addition, when a value of the detection voltage Vdet is
lower than the first threshold voltage Vth1, the controller 22 sets
the control signal CGS as Lo. That is, the controller 22 switches
off the switching device 47 and switches the current regulator 23
to the first state. When a value of the detection voltage Vdet is
higher than or equal to the first threshold voltage Vth1, the
controller 22 sets the control signal CGS as Hi. That is, the
controller 22 switches on the switching device 47 and switches the
current regulator 23 to the second state. In other words, when the
AC voltage VCT is lower than a predetermined value, the controller
22 switches the current regulator 23 to the first state; and when
the AC voltage VCT is higher than or equal to the predetermined
value, the controller 22 switches the current regulator 23 to the
second state.
[0084] In addition, when the type of the conduction angle control
is determined as phase control, the controller 22 delays a time
when the current regulator 23 is switched from the first state to
the second state to be slower by a first micro time MT1 than a time
when a voltage value of the detection voltage Vdet is switched from
the state of being lower than the first threshold voltage Vth1 to
the state of being higher than or equal to the first threshold
voltage Vth1.
[0085] For example, it is assumed that a triac is used for the
dimmer 3 which performs the conduction angle control using phase
control; and an LED is used as the illumination light source 16. A
consumption current of the LED is lower than that of an
incandescent lamp or the like. Therefore, unless the
above-described operation is performed, a holding current, which is
required for turning on the triac when the AC voltage VCT is lower
than or equal to a predetermined value, cannot flow. Therefore, the
operation of the dimmer 3 may be unstable.
[0086] On the other hand, in the power supply circuit 14 according
to the embodiment, by controlling the operation of the current
regulator 23 as described above, the holding current, which is
required for turning on the triac when the AC voltage VCT is lower
than or equal to a predetermined value, can flow to the current
regulator 23 (to the branch path 27). As a result, the operation of
the dimmer 3 can be stabilized. In addition, by delaying the
switching time of the current regulator 23 by the first micro time
MT1, the operation of the dimmer 3 can be further stabilized.
[0087] When the current regulator 23 is in the second state, the
power is not supplied to the controller power supply 24.
Accordingly, when the type of the conduction angle control is
determined as phase control, the power is not supplied to the
controller power supply 24 in a period obtained by decreasing the
conduction period Ton by the first micro time MT1. In this way,
when the type of the conduction angle control is determined as
phase control, the controller 22 switches the current regulator 23
to the second state and decreases the power supply to the
controller power supply 24 in at least a part of the conduction
period Ton. For example, the controller 22 stops the power supply
to the controller power supply 24.
[0088] When the type of the conduction angle control is determined
as phase control, in the blocking period Toff and the period of the
first micro time MT1, a voltage is input to the regulator 53 and
the backup capacitor 54; and the regulator 53 operates due to the
input voltage. On the other hand, in the remaining period (period
obtained by subtracting the first micro time MT1 from the
conduction time Ton), the regulator 53 operates due to charges
accumulated in the backup capacitor 54.
[0089] FIGS. 5A to 5C are graphs schematically illustrating an
operation of a controller according to an embodiment.
[0090] FIGS. 5A to 5C illustrate an operation example of the
controller 22 when the type of the conduction angle control is
determined as reverse phase control.
[0091] The horizontal axis and the vertical axis of FIGS. 5A to 5C
are the same as those of FIGS. 4A to 4C.
[0092] As illustrated in FIGS. 5A to 5C, when the controller 22
determines the type of the conduction angle control as reverse
phase control, first, the controller 22 also detects the conduction
angle of the AC voltage VCT. For example, the controller 22
determines a period in which the detection voltage Vdet is higher
than or equal to the first threshold voltage Vth1 as a conduction
period Ton for the conduction angle control of the dimmer 3. In
addition, the controller 22 determines a period in which the
detection voltage Vdet is lower than the first threshold voltage
Vth1 as a blocking period Toff for the conduction angle control of
the dimmer 3. As a result, the controller 22 detects the conduction
angle of the AC voltage VCT based on a ratio of the conduction
period Ton and the blocking period Toff.
[0093] After detecting the conduction angle of the AC voltage VCT,
the controller 22 generates the dimming signal DMS with a duty
ratio corresponding to the conduction angle and inputs the
generated dimming signal DMS to the overcurrent protection unit 25.
As a result, the illumination light source 16 can be dimmed
according to the AC voltage VCT of which the conduction angle is
controlled by reverse phase control.
[0094] When a value of the detection voltage Vdet is lower than the
first threshold voltage Vth1, the controller 22 sets the control
signal CGS as Lo and switches the current regulator 23 to the first
state. When a value of the detection voltage Vdet is higher than or
equal to the first threshold voltage Vth1, the controller 22 sets
the control signal CGS as Hi and switches the current regulator 23
to the second state.
[0095] In addition, when the type of the conduction angle control
is determined as reverse phase control, the controller 22 advances
a time when the current regulator 23 is switched from the second
state to the first state to be faster by a second micro time MT2
than a time when a voltage value of the detection voltage Vdet is
switched from the state of being higher than or equal to the first
threshold voltage Vth1 to the state of being lower than the first
threshold voltage Vth1.
[0096] For example, the controller 22 stores a time of the
half-wave conduction period Ton which is detected in the previous
cycle; and switches the current regulator 23 from the second state
to the first state at a time which is faster by the second micro
time MT2 than the time of the half-wave conduction period Ton.
[0097] In reverse phase control, due to the effect of charges
accumulated in the filter capacitor 36 or the like, the conduction
period Ton may be longer than the actual conduction period of the
dimmer 3. When the conduction period Ton is longer than the actual
conduction period, for example, the duty ratio of the dimming
signal DMS changes; and the dimming degree of the illumination
light source 16 changes.
[0098] By setting the current regulator 23 to the first state and
causing a part of a current flowing through the first power supply
path 26a to flow to the branch path 27, the charges accumulated in
the filter capacitor 36 or the like can be drawn to the current
regulator 23. As a result, in the power supply circuit 14, the
conduction angle of the AC voltage VCT subjected to reverse phase
control can be more reliably detected. The illumination light
source 16 can be dimmed with higher precision. In addition, as
described above, by advancing the switching time of the current
regulator 23 by the second micro time MT2, the charges accumulated
in the filter capacitor 36 or the like can be more appropriately
drawn. The detection precision of the conduction angle can be
further enhanced.
[0099] When the type of the conduction angle control is determined
as reverse phase control, the power is not supplied to the
controller power supply 24 in a period obtained by decreasing the
conduction period Ton by the second micro time MT2. In this way,
when the type of the conduction angle control is determined as
reverse phase control, the controller 22 switches the current
regulator 23 to the second state and decreases the power supply to
the controller power supply 24 in at least a part of the conduction
period Ton. For example, the controller 22 stops the power supply
to the controller power supply 24.
[0100] When the type of the conduction angle control is determined
as reverse phase control, in the blocking period Toff and the
period of the second micro time MT2, a voltage is input to the
regulator 53 and the backup capacitor 54; and the regulator 53
operates due to the input voltage. On the other hand, in the
remaining period (period obtained by subtracting the second micro
time MT2 from the conduction time Ton), the regulator 53 operates
due to charges accumulated in the backup capacitor 54.
[0101] For example, it is assumed that there is a power supply
circuit which supplies power to a controller power supply in all
the phases of an AC voltage. In such a power supply circuit, a
current flows to the controller power supply, for example, even in
a phase angle period which is unnecessary for dimming; and the
power loss of the power supply circuit is huge.
[0102] On the other hand, in the power supply circuit 14 according
to the embodiment, the conduction angle of the AC voltage VCT is
detected; and the power supply to the controller power supply 24 is
decreased in at least a part of the conduction period Ton of the
detected conduction angle. In addition, at least when the AC
voltage VCT is switched from the conduction period Ton to the
blocking period Toff, the power is supplied to the controller power
supply 24. As a result, in the power supply circuit 14, power loss
can be suppressed. In addition, by suppressing power loss, heat
generation of the power supply circuit 14 can be suppressed.
[0103] In addition, in the power supply circuit 14, in the case of
phase control, the backup capacitor 54 is charged with a current
for causing the holding current to flow to the triac of the dimmer
3; and in the case of reverse phase control, the backup capacitor
54 is charged with a current for drawing charges from the filter
capacitor 36 or the like. As a result, power loss can be more
appropriately suppressed.
[0104] In addition, in the power supply circuit 14, the constant
power circuit 58 is provided on the controller power supply 24 such
that power consumed in the controller power supply 24 is made to be
substantially constant. As a result, for example, when an input
voltage is high (when the absolute value of the AC voltage VCT is
high), an increase in power loss can be suppressed. The power loss
of the power supply circuit 14 can be more appropriately
suppressed. The constant power circuit 58 is not limited to the
above-described circuit and may be any circuit capable of making
the power consumed in the controller power supply 24 substantially
constant.
[0105] Hereinbefore, the embodiments are described using the
specific examples. However, the embodiments are not limited
thereto, and various modifications can be made.
[0106] The illumination light source 16 is not limited to an LED.
For example, organic electro-luminescence (organic EL) or organic
light-emitting diode (OLED) may be used. In the illumination load
12, plural illumination light sources 16 may be connected to each
other in series or in parallel.
[0107] In the above-described embodiments, the illumination load 12
is described as a load. However, the load is not limited thereto.
For example, a heater or other loads may be used. In the
above-described embodiments, the power supply circuit 14 which is
used for the illumination apparatus 10 is described as a power
supply circuit. However, the power supply circuit is not limited
thereto. For example, any power supply circuit corresponding to a
load may be used. In addition, a voltage which is supplied to a
load is not limited to a DC voltage. For example, an AC voltage or
a ripple voltage may be used.
[0108] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of the inventions. Indeed, the novel
embodiments described herein may be embodied in a variety of other
forms; furthermore, various omissions, substitutions and changes in
the form of the embodiments described herein may be made without
departing from the spirit of the inventions. The accompanying
claims and their equivalents are intended to cover such forms or
modifications as would fall within the scope and spirit of the
inventions.
* * * * *